You have created a managed software delivery package, and you want to allow users to defer the installation a specific amount of time.
IT Management Suite (ITMS) 8.5 RU1 and later
After you have created a policy for the managed delivery of a software package you will see:
Click on the "Advanced options" button.
Click the boxes for:
Then select the time unit you want (minutes, hours, days) and then the number.